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General Session 2: Marine & estuarine biogeochemistry |
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Diazotrophs in West Philippine Sea under influence of mesoscale eddies
GS2-69-S
Cheung Shunyan* , Division of Life Science, The Hong Kong University of Science and Technology
Xia Xiaomin, Division of Life Science, The Hong Kong University of Science and Technology
Liu Hongbin, Division of Life Science, The Hong Kong University of Science and Technology
Presenter Email: sycheungab@ust.hk
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| Nitrogen fixation is an important source of new production in subtropical North Pacific Ocean. However, the community composition and limiting factors of the diazotrophs in the subtropical Western North Pacific Ocean (WNPO) is still not known. In this study, we reported the diazotrophic community structure, as well as the abundance and activities of the important phylotypes in the highly dynamic West Philippine Sea (WPS) of the WNPO, using 454-pyrosequencing and quantitative PCR (qPCR). In community level, Unicellular cyanobacteria UCYN-A2 was predominant in coastal water, while UCYN-A1 and Gammaproteobacteria γ-24774A11 were predominant in oceanic water. Trichodesmium was predominant in Kuroshio Current (KC), warm eddy and cold eddy. Surprisingly, based on the qPCR result, the abundance of UCYN-A2 remained stable along the transect, with significant abundance (104 gene copies per liter) in the oceanic stations. In cDNA level, Trichodesmium andγ-24774A11 contributed majority (> 90 %) of the nifH transcripts in the WPS. In addition, we have detected a bloom of Trichodesmium (108 gene copies per liter) in the cold eddy, and the abundance of Trichodesmium in the study area was strongly and positively correlated with iron concentration (r = 0.84, p-value < 0.05, n = 8). Our results suggested that cold eddy may play an important role in nitrogen fixation process in subtropical WNPO. |
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